1. Field of the Invention
A method for synthesizing chiral allylic alcohols is disclosed. More specifically, paired chiral diols that are anti (on opposite sides) or syn (on the same side) were generated by aldol reactions between selones (aldol acceptor) and various aldehydes (aldol donor).
2. Description of the Background Art
Aldol reactions have played a central role in many stereoselective constructions of carbon-carbon bonds. Evans reported in 1981 that a boron based enolate of an N-acylated 2-oxazolidinone underwent stereoselective carbon-carbon bond formation with aldehydes to give a syn aldol product.1 
An object of the present invention is to provide a method of synthesizing 1,2-diol units.
Another object of the present invention is to disclose a method for producing an optically active or chiral 1,2-diol unit within a molecule.
A further object of the present invention is to relate a process for making chiral 1,2-diol containing molecules via an aldol reaction between a selone (aldol acceptor) and an aldehydes (aldol donor).
Still another object of the present invention is to describe a chiral 1,2-diol synthesis scheme that utilizes an aldol donor, an aldol acceptor, a Lewis acid, and a suitable amine under acceptable conditions.
Yet a further object of the present invention is to present synthesis scheme for making a chiral 1,2-diol that employs an aldehyde, an N-acyl selone prereacted with TiCl4, and diisopropylethylamine under reaction producing conditions.
Generally, disclosed is a synthesis method for making chiral 1,2-diols from reactions between an aldehyde and an N-acyl selone. Chilled N-acyl selone is reacted with a Lewis acid and mixed with a suitable amine to generate an enolate solution. The temperature range for this reaction is from about room temperature to about xe2x88x9250xc2x0 C., but may be higher or lower depending upon the reactants, but preferably between about room temperature and about xe2x88x9230xc2x0 C. and more usually about 0xc2x0 C. to about xe2x88x9215xc2x0 C. Upon further chilling of the enolate solution a desired aldehyde is added and after an acceptable reaction period a quencher is introduced and the product isolated. The further chilling is to a temperature range of about room temperature to about xe2x88x92100xc2x0 C. and usually about room temperature to about xe2x88x9290xc2x0 C., although colder temperatures may be required depending upon the reactants, more usually about room temperature to about xe2x88x9280xc2x0 C. (this temperature may in some cases vary during the time of the reaction).
More specifically, disclosed is a method comprising the steps of: obtaining an aldol donor or aldehyde; obtaining an aldol acceptor or N-acyl selone; generating the Lewis acid enolate of the N-acyl selone by adding the selected Lewis acid to the chilled solution of the N-acyl selone with the subsequent addition of a suitable amine, preferably a tertiary amine; cooling the combined mixture further and adding the aldehyde; allowing the combination to react until complete; quenching the reacted combination; and isolate the product.